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Re: pg_dump & performance degradation

From: Philip Warner <pjw(at)rhyme(dot)com(dot)au>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org, brianb-pggeneral(at)edsamail(dot)com
Subject: Re: pg_dump & performance degradation
Date: 2000-07-28 16:52:57
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Lists: pgsql-generalpgsql-hackers
At 12:22 28/07/00 -0400, Tom Lane wrote:
>Philip Warner <pjw(at)rhyme(dot)com(dot)au> writes:
>> Brian Baquiran in the [GENERAL] list recently asked if it was possible to
>> 'throttle-down' pg_dump so that it did not cause an IO bottleneck when
>> copying large tables.
>> Can anyone see a reason not to pause periodically?
>Because it'd slow things down?


>> Finally, can anyone point me to the most portable subsecond timer routines?
>You do not want a timer routine, you want a delay.  I think using a
>dummy select() with a timeout parameter might be the most portable way.
>Anyway we've used it for a long time --- see the spinlock backoff code
>in s_lock.c.

Well...pg_dump sits in a loop reading COPY output; my hope was to see how
long the copy took, and then wait an appropriate amount of time. The dummy
select works nicely as a sleep call, but I can't really tell how long to
sleep without a sub-second timer, or something that tells me the time
between two calls.

Would there be a portability problem with using setitimer, pause, & sigaction?

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